With the Missouri River basin experiencing prolonged wet conditions, two area dams will maintain historic high flows into September.
The U.S. Army Corps of Engineers announced Thursday it will not step down the releases at Gavins Point Dam near Yankton or Fort Randall Dam at Pickstown.
The Corps had previously announced the current releases —among the highest in the 60-year history of the dams — would run through August.
The Corps has maintained releases of 70,000 cubic feet per second (cfs) for weeks, even briefly reaching 100,000 cfs last March. Those figures trail only the record 160,000 cfs during the 2011 Missouri River flooding.
The current unchanged basin conditions have forced the continuation of the current high flows into next month, said Mike Swenson, a hydraulic engineer with the Corps in Omaha.
In a conference call, Swenson alluded to the continued heavy rainfall and saturated soil that continues to fill the Missouri River reservoirs.
“Soils are still very wet across much of the basin,” he said. “Gavins Point releases are currently 70,000 cfs. Our latest reservoir studies indicate holding the 70,000 cfs release through September.”
During a rapid influx of water last March, the Corps was forced to increase its Gavins Point releases several times in a matter of hours. At one point, the Corps released 100,000 cfs for six hours.
The rapid Missouri River flooding occurred when a bomb cyclone hit the region and the Spencer Dam, which controls the Niobrara River, breached in northeast Nebraska. The one-two punch dumped an 11-foot wall of water and ice jams between Fort Randall and Gavins Point, the last of the six mainstem dams.
Fort Randall Dam will maintain flows of around 66,000 cfs, Swenson said.
The Missouri River continues to see minor flooding, while the James River and Big Sioux River also see continued flooding in South Dakota, said Kevin Low with the Missouri Basin River Forecast Center of the National Weather Service.
The southern Missouri River basin could see one and even two rounds of heavy rainfall during the next week, Low said in the conference call.
The rainfall would not only worsen local flooding, but it could also prevent the Corps from making major progress in vacating water from the reservoirs.
“We expect a very active pattern over the southern basin over the next seven days. The front is setting up over southeast Nebraska with several bouts of heavy rain (Thursday) and through the weekend. We could have widespread 2-3 inches average through the weekend,” he said.
“There are some locations that could see in excess of 5 inches before this event ends on Sunday. We will get a respite for about 48 hours before the second system builds on Wednesday. We’ll get rain on Wednesday and Thursday across the southern part of the basin.”
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